Just days before a Maryland couple was found dead in their Dominican Republic hotel room, a different American tourist died at the same resort.

According to NBC News, 41-year-old Miranda Schaup-Werner, of Allentown, Pennsylvania, died in her room at the Luxury Bahia Principe Bouganville on May 25.

Schaup-Werner and her husband were vacationing on the island to celebrate their ninth wedding anniversary. Schaup-Werner’s family told NBC she died from respiratory failure and pulmonary edema, the same cause of death as engaged couple Nathaniel Holmes, 63, and Cynthia Day, 50.

Five days after Schaup-Werner’s death, Holmes and Day were found dead in their hotel room at the Grand Bahia Principe La Romana, a neighboring resort on the same property.  

In a statement to NBC, the U.S. Department of State confirmed the death, but did not confirm the cause of death. The department also did not state any connections between the deaths.

Schaup-Werner's brother-in-law, Jay McDonald, told NBC she had “a drink from the in-room minibar. Her husband, Dr. Daniel Werner, was with her when she abruptly experienced acute physical distress and collapsed.”

McDonald also said his sister-in-law was in good health.

The sudden and shocking deaths of all three U.S. citizens have alarmed their relatives, who are demanding more information.

McDonald told NBC he doesn’t see how a "healthy 41-year-old suddenly dies like this," adding that no officials in the Dominican Republic performed a toxicology report, nor did they test Schaup-Werner's glass and drink.

In his statement, McDonald asked, “Why didn’t the deaths of the Maryland couple trigger an investigation, following so closely on Mrs. Schaup-Werner’s death? Have there been other deaths?”

Investigators are currently working to determine if carbon monoxide poisoning caused the deaths of Holmes and Day. Officials in the Dominican Republic have not stated whether the couple’s room had a carbon monoxide detector.

The families of Day and Holmes plan to have independent autopsies conducted on the bodies once they are returned to the U.S.